Schizophrenia (SZ) is a common, chronic group of psychotic brain disorders, affecting 1% of the US population, creating a significant public health problem because of the associated disability, morbidity and mortality. The pathogenesis of SZ is poorly understood, but it is thought to be a neurodevelopmental disorder. Neuroimaging evidence has accumulated to indicate that the dorsolateral prefrontal cortex (DLPFC) functions abnormally in SZ, both when activated and at rest. Further, EEG evidence has identified abnormalities of ? oscillations in SZ, suggesting that parvalbumin positive GABAergic interneuron regulation of cortical pyramidal neurons is dysfunctional. In the past 5 years, data have accumulated to prove that activation of LINE1 (L1) retrotransposons (RTPs) may occur wherever chromatin assumes a relaxed state to permit transcriptional activation. The abnormal DLPFC activation and ? oscillations in SZ may drive chronic aberrant transcriptional activation, thereby providing opportunities for L1s to retrotranspose in the developing CNS. These somatic de novo L1s may interfere with normal neuronal activity because they have inserted into a gene needed by that neuron for normal function. If one or more functional de novo L1s occur early in CNS development, all the daughter neurons that derive from that neuronal precursor will also carry the L1, perhaps leading to a dysfunctional population of neurons destined to increase risk for SZ. This project builds on preliminary results indicating that intragenic de novo L1s are found significantly more often in SZ DLPFC neuronal DNA in relevant gene ontologies (eg, synapse part and plasma membrane part; p = ~10-4), compared to control tissue. This proposal will employ DLPFC and anterior cingulate tissue (obtained at autopsy) from 100 SZ patients and 100 matched controls. Using differential centrifugation and fluorescence assisted cell sorting (FACS), followed by PCR to enrich the DNA for L1 sequences, DNA amplicons will be sequenced and aligned to the reference genome to detect intragenic de novo (not in the reference genome) L1s in brain-expressed genes. Allele frequencies of the most promising intragenic de novo L1s will be estimated by droplet digital PCR. Selected intragenic de novo L1s will be re-created in neuronal cell lines via CRISPR/Cas9 technology. The functional effect of the de novo L1 on transcription and translation of the gene will be determined. In this manner, it is expected that intragenic de novo L1s, which increase risk for SZ, will be discovered.